High sensitivity vibration estimation using pulse echo Doppler ultrasound

Two methods are developed for detecting tissue vibration produced in vibro-acoustography using pulse echo ultrasound. The tissue vibration generated by the oscillatory radiation force is detected in echoes of repetitively transmitted ultrasound pulses. The Normalized Magnitude Difference (NMD) method detects the oscillatory Doppler shifts and estimates the amplitude of the vibration. The quadrature method is developed to extract the vibration information from modulated ultrasound signals. The quadrature method estimates both amplitude and phase of the vibration. Vibration with a displacement less than 30 nm has been detected. Phase estimates are excellent if signal-to-noise ratio is high enough.